Heat coil



AJuly 31, 1928.

d J. s. BAKER.

HEAT COIL apt. 27. 1322 Filed S Patented duly 3l,

c liliana@ ,A TURN S. BAKER, 0F CHCAGU, ELLNOIS, ASSIGNOR TO THE @00K ELECTRGCGMPANY,

GHICAGU, ILLINS, A CREORATEEON 03F IJLINES,

HEAT @GIEL Application nled September 2'?, i922. Serial No. httt.

My invention relates to protective devices for electrical circuits and it has special refer ence to heat coils of the sell-soldering type.

'll-leat coils have heretofore been employed extensively as protective devices against cause of the poor thermal relations existing between their various elements. For instance, the resistance windings or heat producing means or the heat coils that areA capable ot generating relatively small amounts of heat are not thermally insulated to a sufficiently high degree from the other metallic parts comprised in the. heat coils, as well as the metallic vvsupports upon which the heat coils are mounted and, consequently, the heat so generated has been ineectively dissipated.

'ln my present invention, ll have produced a heat coil which will be economical and simple to construct and which will respond readily to excess current conditions obtaining in the circuit that the heat coil is adapted to rotect.

fin object, therefore, of mv present invention is to provide a sell-soldering heat coil in which substantially all ci the heat developed in the heat producing means or resistanceV winding is edective in acting upon a self-soldering joint or heat responsive element whereby the heat coil will actuate with quick response to protect the associated electrical circuit.

Another object of my invention-is yto provide a sell-soldering heat coil of the character indicated above in which the responsive element, While being in very close thermal relation to the heat producing-means orresistance winding, is subject to minimum mechanical stress which insures that the .heat coil will remain permanenti in operative condition without becoming atigued.

Other objects of my invention will hereinafter appear. and for a better understanding of the nature, scope and characteristic features of my present invention, reference may be had to the following description and the accompanying drawing, in which- Figure l illustrates heat coils :forming a part ot my invention positioned in aspring supporting plate .of a telephone frame;

llg. 2 is a cross-sectional view showing the deta1led construction of a heat coil embodying a torni oit my invention; .Figa 3 is a plan view ci the device ot llig.. 2; Y Y

Fig. 4r is a perspective view showing the construction. of the centrallsupporting memberupon which the resistance coil is wound;

and v Fig. 5 is a perspective view showing the main central supportitor the heat coil.

Referring to ligure' l, spring supports of a common torni of construction are shown whlch are provided wit-h suitable groundin arresters 12 that constitute carbon blocksY spaced trom each other by means of a dielec-` tric insulating material. The' lightning arresters l2 are of a well-known type of conterminals l and 'il and with lightning. 7u

struction. Heat coils 13 and le are mounted 75 in brackets l and i6 respectively which are secured to a supporting trame lig The apparatus oi Fig. l is adapted for ,use in telephone systems and :termsterminals tor' telephone lines, switchboard'and alarm cir- 80 cuits. -ll`he heat coil i3 shows itsratchet wheel in normal operating condition whereby f a spring member 18 is heldin disengage-v ment from the 4grounding terminal ll.'

When the heat coil operates, the spring i8 e5 will be released and assume a position corresponding to that shown by a spring mern-y ber i9 associated with the heat coil la, 'lhe spring member 19 is released when the ratchet wheel Ma oit the heat coil ld is per- @o l l mitted to rotate, which condition obtains when the heat coil is subjected to an excess temperature arising from the iow of y 6snealt currents against which the heat coils 13 and 14 are designedto protect the 915 i telephone apparatus.4 The mechanism ot Figure l, .excepting the heat coils, is old inv the art and, therefore, further description is not deemed necessary. l Referring to Fig. 2 the heat coil embodying a torni ofmy present'invention comprises a main central supporting member 20 which is provided. with a threaded end 21a, By means ont this threaded end the heat coil is mounted in the support upon the telephone rack of Fig. l. rEhe main supporting pin orA member 20 is encircled by a heat conducting cylindrical member 21 but is thermally insulated therefrom by an interposed dead air space 22. 'Ihe member 21 is made as light as possible so that its heat abso-rptive capacity will be very small, and is provided with an extension or sleeve 22L upon which an actuator or lratchet wheel 23 is mounted. The ratchet wheel 23 is provided on its periphery with teeth 2li. rllhro'ugh the medium of these peripheral teeth the spring members 18 and 19a of the mechanism of llig. 1 may be held against the pins 11:"- and 10a. 'Ihe ratchet wheel 23 is secured to the sleeve 22 by means of a heat responsive element, such asa fusible joint 25, that is' preferably made of solder. rl'Che solder joint 25 is adapted to respond in a very short interval of time to anyexcess' current ilowing in al current conducting resistance coil 26 that is wound upon the cylindrical member 21.

'llhe main supporting pin 20 is provided adjacent to its threaded end 21a with 'a hanged extension 27 such as shown in ligure 5. rlheV flanged extension 27 has three spacedV and integrally formed ears 28 which are adapted to be received in notches formed in the lower edge of an insulating bushing 29 that houses the resistance coil 26 and the cylindrical memben, 21. By means of the ears 28 the insulating casing 29 is held in fixed relation with reference to the main supporting pin 20. Likewise, thecylinolrical member 21 is provided with a plurality of integrally formed and spaced ears 30 which engage the insulating sleeve 29 at its upper edge.

A fibre washer 31 may be interposed between the cylindrical member 21 andthe metallic flange 27 of the main supporting member 20. Similarly, a fibre washer 32 embraces the upper-end of the main supporting pin'20 and holds in spaced relation the sleeve 22a from the supporting pin 20. One end of the resistance coil 26 is soldered at 33 to the main supporting pin and the other end is soldered at 34 to the cylindrical member 21. In this manner, the ratchet Wheel 23 becomes one terminal for the current conducting `coil 26 and is insulated from the terminal 33 or the main supporting pin 2O by means of the fibre washer 32 and the dead space 22.

From the foregoing description, it will be observed that the cylindrical member 21 is thermally insulated from the main supporting member and, at the same time, is composed of as small a mass as is consistent with mechanical strength. The fusible connection is in close thermal relation to the resistance coil 26 and, as a consequence, the heat developed by the resistance coil 26 is readily and quickly conducted to the fusible or soldered connection 25. i When th-e fusible connection 25 becomes heated to the point where net/aseo it is liqueed, the ratchet wheel 23 may move relative tothe sleeve 22. In this circumstance, the spring member 19a of Fig. 1 is released from the heat coil 1d and the terminal 19 is grounded.

l have discovered that a soldered joint on being subjected to a continuous stress or strain in its cold state becomes fatigued and, in time, will shear thereby releasing. any parts that may be connected together thereby. By reducing the unit stress upon a soldered joint, it is relieved of undue mechanical fatigue and, therefore, is, not likely to shear. ll lower the mechanical stress imposed upon the soldered jointin my present heat coil by disposing the soldered joint 25 at a considerable radius fromthe main supporting pin 21. rllhis not only gives an increased area for the soldered joint, but also provides a decreased leverage and consequentA resisting forcefor the soldered joint. j

The resistance coil 26 is positioned in close thermal relation to the soldered jointV 25 and by reason of the small mass of the cylindrical member 2l, most of the heat generated by the resistance coil is conducted readily in proximity to the soldered joint 25. rlhe central supporting pin 21, which is of considerable mass and also in close contact with the heavy metallic supporting frames of the telephone rack, is effectively heat insulated from the resistance coil 26 by means of the air space 22. rllhe nbre washer 32 and the fibre cylinder 29 which enclose the heat resistance coil 26 are poor conductors of heat and, therefore, substantially all of the heat generated is permitted to accumulate in the mass of the cylindrical member 21;)

When an abnormal current flows through the resistance coil 26, the fusible connection 25, which is preferably made of solder, liqueties and permits relative action between the actuator or ratchet wheel 23 and the cylindrical member 21. When the current re- "duces to a normal value, the soldered convspirit and scope of the appended claims.

What I claim as new and desire to secure `by Lettersy Patent of the U. S. is:

1. A heat coil comprising a main supporting member, a second member surrounding 1 said main member and thermally insulated therefrom, heat producingj'means upon said second member, al1-actuator, a fusible material securingV said actuator to said second member whereby, when the fusible material is softened, the said actuator may move relatively to said second member.

2. A heat coil comprising a main Supinvaso@ said main member and thermally insulated therefrom, heat producing means upon said second member, a ratchet wheel mounted upon said second member, a 4fusible material securing said ratchet wheel to said second member whereby, when the fusible material.

is softened, the said ratchet wheel may move relatively to said second member.

4. A heat coil comprising a main supporting pin, a second member surrounding said pin but thermally insulated therefrom, a resistance coil wound uponsaid second member, a ratchet wheel `mounted upon said second member, a fusible connection between said ratchet wheel and said second member whereby, when the fusible material is softened, the said ratchet wheel may rotate upon said second member.

.5. A heat coil comprising a main supporting member extending centrally therethrough, a second member mounted about andthermally insulated from said. supporting member, a resistance coil wound upon Vsaid second member, an actuator, and heat responsive means in close thermal relation to said resistance coil whereby, when the heat responsivemeans becomes excessively heated, the said actuator may move freely. 6. A heat coil comprising a main supporting member, a concentrically disposed second member thermally insulated therefrom, heat producing means upon said second member, an actuator in close thermal relation to said heat producing means, and heat responsive means' normally securing said actuator to'said second member whereby, when the heat responsive means becomes eX- cessively heated, the said actuator may move relatively to said second member, said heat responsive means automatically securing together said actuator and said second member when the excess heat in the heat responsive means is dissipated.

7.' heat coil comprising a central supporting member, a" heat conducting cylindrical member thermally insulated from vsaid supporting member, a resistance coil uponI said cylindrical member,` a ratchet wheel in close thermal connection with said cylindrical member,I and a fusible material mechanically connecting said ratchet wheel to said 4cylindrical member.

8. A heat coil comprising a main supporting pin, a cylindrical member encircling` said pin and thermally insulated therefrom, a

currentcarrying coil mounted upon said cylindrical member, a ratchet wheel mounted on saidcylindrical member, a fusible connection between said ratchet wheel and said cylindrical member in close thermal relation to saidcoil, and a casing of low heat conductivity for said coil.

9. A heat coil comprising a central supporting pin, a heat insulated casing mounted thereupon, a heat conducting member positioned interiorly of said casing and exteriorly of said supporting pin and thermally insulated therefrom, a resistance coilwound upon said heat conducting member, a ratchi et wheel mounted upon said conducting member and exteriorly ofsaid casing, and a fusible connection between said ratchet wheel and said heat conducting member and in close thermal relation to said resistance co1 Y A l0. Il. heat coil comprising a supporting member, a substantially hollow cylindrical member of small mass thermally insulated therefrom, heat producing means upon said hollow cylindrical member, an actuator in close thermal relation to said heatprodueing means, and heat responsive means normally securing said actuator to said hollow cylindrical member whereby, when the heat responsive means becomes excessively heated, the said actuator may move relatively to said hollow cylindrical member, said heat responsive means automatically securing together said actuator and said hollow cylindrical member when the excess heat in the heat responsive means is dissipated.

l1. A heat coil comprising a,.,main supporting member, a second member thermally insulated therefrom, ya resistance coil wound upon said second member, an actuator, and heat responsive means in close thermal relation to said resistance coil whereby, when` the heat responsive means becomes excessively heated, then only may the said actuator move.

12. A heat coil comprising a supporting pin, an actuator, a mounting for said actuator, and thermal insulating means for interlocking said pin andL said mounting together, said means, pin and mounting being arranged in concentric'relation with respect lto each other.

13. A'heat coil comprising a central supporting pin, an actuator, a mounting for said actuator spaced in concentric relation to said pin, and thermal insulating means. for interlocking said pin and said mounting together. l.

1 4. A heat coil comprising a central supporting pin, an' actuator, a mounting for said actuator spaced in concentric relation to said pin, a heat responsive connection belll@ raaf

tween seid mounting and .seid noti/into?, and thermal insulating means tot inteiiocking said pin and said mounting together.

l5. A heet ooit comprising n centini supporting pin, en actuator, n mounting" tot' said actuator spaced in concenti'io relation. to said pina and means tot' inteiiooking said pin and .said mountin together'a seid ineens comjpi'ising` an insulating sleeve disposed eX- tetioily ont said mounting.,

i6, it heet ooit comprising u centred suppotting pin, en actuator, n mounting for seid actuator spaced in concentric relation to said pin, said pin end seid mounting being provided With spaced interni extensions, and at notched sleeve engaging said exten sions for interlocking saidA pin and said. mounting togethen7 En Witness whereof, have hei'eunto suhsciibed my nume.

JHN S. BAKER. 

